3D Rigging Pipeline (Blender/bpy Authoring)

Scope boundary — read this before anything else

• This skill = AUTHORING. Headless Blender/bpy: computing, baking, and exporting a correction or a rig.
• threejs-animation = RUNTIME. Wiring morph-target influence during three.js playback in the browser. It already names this skill by this exact name for the Blender-side half of the same problem (threejs-immersive.md in skyyrose-wp-platform cross-references it).
• Render-QA / mockup-pipeline skills = POST-EXPORT. Output-fidelity grading after a GLB already exists.
• Hand off at the GLB file boundary. Never duplicate another skill's half of the problem.

When to use

Use when any of these is observably true:

• A .blend or .glb under renders/3d/ needs a rig, a re-weight, a corrective shape key, or a re-export — e.g. renders/3d/girl-love-hurts/love-hurts-girl-rig.blend.
• A mesh shows LBS candy-wrapper collapse, an armpit/elbow crease defect, or a shape key leaking a nonzero rest weight into the exported GLB.
• You are about to retarget a walk/idle clip from one armature onto another and have not yet run the rest-direction precondition gate.
• A rigged GLB is about to ship and has not been draco-compressed / texture-normalised.

Do NOT use when:

• The defect appears only during browser playback and the GLB itself is clean — that is threejs-animation (runtime morph wiring), not this skill.
• The question is "does this render look like the right garment/character" — that is the render-QA / product-image-fidelity gate, which reads pixels, not bones.
• You only need to view a GLB. Reading a file is not authoring.

Inputs

Required before starting	How to confirm it	If absent
The target .blend / .glb, by real path	ls -la renders/3d/<character>/	STOP. Never author against a path you have not listed. Never create a placeholder mesh to "unblock".
A reference/backup of the pre-edit file for any non-idempotent script	ls renders/3d/<character>/*backup*.blend + md5	STOP. add_armpit_gusset.py-class scripts are non-idempotent; a blind re-run silently double-applies.
Blender available headless, when a step imports bpy	blender --version	STOP for that step. The pure-python gates in scripts/ do NOT need Blender and can still run — say which half is blocked, do not report the whole task blocked.
npx @gltf-transform/cli reachable, for export checks	npx @gltf-transform/cli --version	STOP the export-verify step. A bare gltf-transform binary does NOT resolve in this environment — it maps to a different, nonexistent npm package.

Absent input is a stop, never a default. A gate that runs against a substituted input is the fail-open pattern (bug-230, ×6).

Procedure

1. Read the doctrine first. reference/doctrine.md — numeric gates only (a printed number from a real run this session), and verification from a source structurally independent of whatever produced the artifact. No harness grades its own output.
2. List the real files. ls -la renders/3d/<character>/ — every later claim cites a path from this listing, not from memory or a prior writeup.
3. Re-derive, never inherit. Any prior "confirmed" number (a gate result, a bone count, a pass) is re-run against the CURRENT file before you act on it. See the reuse-vs-re-derive table in reference/love-hurts-worked-example.md.
4. Pick the authoring path and read only its reference file:
   • corrective / pose-driven shape keys → reference/shape-keys.md
   • cross-armature retargeting → reference/retargeting.md (run its rest-direction precondition gate BEFORE building any constraint — bug-195)
   • export + compression → reference/export-pipeline.md
5. Run the script, headless. blender -b <file>.blend -P <script>.py for bpy steps. Non-idempotent scripts: md5 the backup first, then run exactly once.
6. Gate the result numerically with the independent checkers in scripts/ (below). A printed number, not an eyeball.
7. Record the outcome — bug id, script, numeric result — in .wolf/buglog.json and .wolf/memory.md in the same change as the fix.

Quick start — locating a mesh's shape keys in bpy

import bpy
mesh_obj = bpy.data.objects["YourMesh"]
if mesh_obj.data.shape_keys:
    for kb in mesh_obj.data.shape_keys.key_blocks:
        print(kb.name, kb.value)  # kb.value == REST/default weight -- must be 0.0 unless
                                   # this key is deliberately held active for a full clip

This is illustrative only — the full corrective-shape-key computation is in reference/shape-keys.md, not here.

Verification

Two independent checks. Both are pure-python/CLI and share no code with the Blender export path, per reference/doctrine.md's independent-authority rule.

1. Export-contract gate — the discriminating one:

cd /Users/theceo/DevSkyy && python3 \
  .claude/skills/3d-rigging-pipeline/scripts/gltf_export_verify.py \
  renders/3d/girl-love-hurts/love-hurts-girl-v1.glb \
  --width 1024 --height 1024 --format jpeg --require-draco

PASS: prints PASS and exits 0 — KHR_draco_mesh_compression present in extensionsUsed/extensionsRequired AND every texture reported at 1024x1024 image/jpeg. Evidence: [repro]

2. Shape-key rest-weight gate — parses the GLB JSON chunk directly, never imports bpy:

cd /Users/theceo/DevSkyy && python3 \
  .claude/skills/3d-rigging-pipeline/scripts/assert_shape_key_rest_weight.py \
  renders/3d/girl-love-hurts/love-hurts-girl-v1.glb

PASS: exits 0 AND the Checked N count is greater than 0 with every rest weight 0.0 (or matching a declared --expect-nonzero override). Checked 0 is NOT a pass — see the SKIP rule below. Evidence: [repro]

A SKIP is not a PASS. Checked 0 shape-key rest weight(s) … PASS means the file carries no shape keys at all: the parser ran, nothing was proven. Treat that as SKIP, name the rigging author as the person who closes it against a GLB that does carry shape keys, and never let it stand in for check 2.

A gate that dies is not a gate that passed. If npx times out, the network is down, or Blender segfaults, the zero-findings output is an artifact — re-run by hand before claiming anything (bug-230).

Attribute before claiming a finding is yours. A defect found in a .glb you just rebuilt may predate your change. Extract the pristine tree and re-run the same gate against it: git archive HEAD renders/3d/<character> | tar -x -C <scratch>. Never git stash — the stash stack is shared across worktrees.

Worked example

Run against the real Love Hurts Girl export, 2026-07-28, in /Users/theceo/DevSkyy:

$ ls renders/3d/girl-love-hurts/*.glb
renders/3d/girl-love-hurts/girl-mascot-raw.glb                 25.5M
renders/3d/girl-love-hurts/girl-mascot-raw.walk-dwell-fix.glb  25.5M
renders/3d/girl-love-hurts/love-hurts-girl-v1.glb              25.5M

$ python3 .claude/skills/3d-rigging-pipeline/scripts/gltf_export_verify.py \
    renders/3d/girl-love-hurts/love-hurts-girl-v1.glb \
    --width 1024 --height 1024 --format jpeg --require-draco
… ANIMATIONS
  0  GirlWalk_Baked   72 channels  72 samplers  duration 1  374 keyframes  5.61 KB
  1  GirlWalk_Source  72 channels  72 samplers  duration 1  374 keyframes  5.49 KB

FAIL -- 3 check(s) did not match:
  KHR_draco_mesh_compression not found in extensionsUsed/Required
  no texture reported at 1024x1024 resolution
  no texture reported with mimeType image/jpeg

Two things this proves at once. (a) love-hurts-girl-v1.glb is a raw, uncompressed export — 25.5 MB, no draco, textures never normalised. It is not shippable to the web as-is; run the reference/export-pipeline.md compression sequence before any theme wires it. (b) The gate itself can return red on a real file — that is rule 3 satisfied by observation, not by assertion. [repro]

The companion run is the honest counter-case:

$ python3 .claude/skills/3d-rigging-pipeline/scripts/assert_shape_key_rest_weight.py \
    renders/3d/girl-love-hurts/love-hurts-girl-v1.glb
Checked 0 shape-key rest weight(s) in …/love-hurts-girl-v1.glb:

PASS -- all rest weights are 0.0 or match a declared --expect-nonzero override.

Checked 0 — this GLB has no shape keys, so the "PASS" proves the parser executes and nothing more. Reporting it as a rest-weight pass would be exactly the fail-open defect this skill exists to prevent. Recorded as SKIP, owner = rigging author, closed only against a shape-keyed GLB. [repro]

Failure modes

Symptom	Root cause	Do this
gltf-transform: command not found	The bare binary maps to a different, nonexistent npm package	Always invoke the scoped package: npx @gltf-transform/cli inspect <file> (documented in scripts/gltf_export_verify.py's docstring)
Retarget produces twisted limbs even though both armatures have identical bone names/hierarchy	Hierarchy match ≠ rest-direction match	bug-195 — run renders/3d/girl-love-hurts/gate_bone_direction.py FIRST. It failed 15/24 bones on this very pair; the build correctly pivoted to a hand-keyframed clip instead of retargeting
Skin-weight self-check reports FAIL on monotonic transitions that are monotonic by construction	Verification sampled ALL vertices with nonzero weight on a bone, mixing two independently-monotonic populations	bug-196 — filter samples to the same chain/segment classification the weighting pass used. A verification checking its own sampling assumption is the self-grading trap
A gusset/mesh edit appears applied twice	add_armpit_gusset.py is non-idempotent, and "pre-existing vertices" recomputed as len(v.groups) > 0 silently widens after run 1	md5 against *.pre-gusset-backup.blend before any re-run; persist the marker as a custom ID property and read it back rather than recomputing
Shape key visibly applied at rest in the browser	Nonzero rest weight leaked through export	Run check 2 above; fix in Blender, re-export, re-run — do not compensate at runtime
A cited "9-phase plan" or "bug-215"	Fabricated citations — neither exists anywhere in this repo	Delete the citation. reference/love-hurts-worked-example.md documents both corrections

What this skill will not do

It will not assert a bug ID, a script's behavior, or a "confirmed" numeric result that wasn't re-derived from a real file or a real script run in the session that touched this skill. Every reference file says explicitly which of its claims are grounded on-disk and which are flagged as unverified — carry that distinction forward, don't flatten it.

Reference files

Read this	For
reference/doctrine.md	The numeric-gate + independent-verification rule every other file inherits
reference/shape-keys.md	Corrective/pose-driven shape keys for LBS candy-wrapper collapse, plus the rest-weight-leak export assertion
reference/retargeting.md	Local-Space Copy Rotation retargeting AND the mandatory rest-direction precondition gate that a real run already needed
reference/export-pipeline.md	The confirmed gltf-transform compression sequence and its --formats gotcha
reference/love-hurts-worked-example.md	The actual, currently-on-disk Love Hurts Girl build — real scripts, not a fabricated phase count

scripts/ holds the runnable checks each reference file calls out by name: assert_shape_key_rest_weight.py, gltf_export_verify.py, lbs_numeric_gate.py, retarget_local_space_gate.py.